There are devices which are more conveniently used if they can be remotely controlled. In a household, such devices are mostly appliances and lighting loads. The appliances and lighting loads may be remotely controlled for a number of different reasons. For example, for night security, some lights may be controlled by a timer. In other cases, different lighting intensity and different lighting distribution may be desirable in a single room, depending upon its use. The room may be used for reading, conversation or watching displays, such as television. Each suggest a different lighting level and different lighting distribution. Normally, people do not make such changes because it is inconvenient to do so. Unless there is a convenient way to accomplish it, such adjustment of the lighting system is rarely done. Therefore, it is desirable to have a convenient, reliable way to remotely control lighting systems.
In addition to lighting systems, other devices can be conveniently remotely controlled. For example, powered gates and garage doors can be remotely controlled. An electric coffee pot may be turned on at an appropriate morning hour. Powered draperies may be opened and closed, depending upon sun altitude.
As electronic technology has advanced, inventors have produced a variety of control systems capable of controlling lighting and other electric loads. In order to be useful as a whole-house lighting control system, there are certain requirements that must be met. A system must permit both small and large groups of lights to be controlled on command. The problem is the connection between the controller and the lighting load. Such connection may be hard-wired, but such is complex and very expensive to retrofit into an existing home. Another connection system may operate at radio frequency, but this has proven difficult to implement because the FCC requires low signal levels which are subject to interference and because the transmission and receiving circuitry is complex and expensive.
It must be noted that both the controller and the load to be controlled are connected to the same powerline. It would be useful to use the powerline as the communication-connecting channel. Prior powerline communication schemes have had difficulties employing the powerline as a communication channel because the communication signals after being attenuated by the powerline circuitry are very small compared to the background noise. It is impossible to avoid the fact that between certain locations in a residence there will be very high attenuation of any transmitted signals. It has been difficult to reliably separate the highly attenuated communication signals from the background noise on the powerline.
The situation is further aggravated and complicated by the fact that the noise and attenuation parameters are constantly and unpredictably changing as loads are connected and disconnected both inside the primary residence and inside any of the many neighboring residences attached to the same mains power transformer. In reality the powerline circuit used for communication in a residence includes all the residences attached to the mains power transformer. There is no practical way to avoid the complications caused by this fact.